Moisture content of paper may be measured by directing infrared light from an optical source to the paper. Interaction between the paper and the infrared light attenuates the power of the infrared light. For example, water attenuates strongly at known, narrow optical bands in infrared region. The attenuation of water depends on the amount of the water in the paper. When an attenuation of an absorption band of water is measured, it is possible to determine moisture content of the measured paper.
When paper comprises colorants such as ink on the surface or inside the sheet the measurement faces serious problems and fails to provide reliable results. Hence, there is a need for a better measurement.